Process for the polymerisation of acrylonitrile



Patented June 2, 1970 Int. Cl. cost 3/76, 15/22 U.S. Cl. 26085.5 12 Claims ABSTRACT OF THE DISCLOSURE Acrylonitrile can be polymerised or copolymerised with other vinyl monomers in solution with a new initiator comprising a peroxy compound, a reducing agent, and a boron compound.

The present invention relates to the solution polymerisation of acrylonitrile.

In order to prepare solutions of polyacrylonitrile which are directly spinnable, it has been proposed to polymerise acrylonitrile in solvents for polyacrylonitrile such as dimethylformamide, dimethylsulphoxide or ethylene glycol carbonate. In this type of polymerisation the most commonly used initiators are azo-bis-isobutyronitrile, ammonium or potassium persulphate, and ultraviolet radiation. It has also been proposed (see French patent specification No. 1,203,479) to polymerise acrylonitrile in solution in dimethylformamide at 30 to 80 C., using, as initiator, acyl peroxides such as lauroyl or butyryl peroxide. However, hydroperoxides, hydroxy-hydroperoxides and per-esters do not for practical purposes initiate the solution polymerisation of acrylonitrile under the same conditions.

A new initiator system comprising a peroxy-compound has now been found which makes it possible to initiate the polymerisation of acrylonitrile with peroxides which, by themselves, are inactive, or to boost the initiating power of peroxides which, by themselves, are only relatively weak initiators.

The new initiators comprise: (a) a peroxy compound, which may be an inorganic compound such as hydrogen peroxide or an organic compound such as a hydroperoxide, hydroxy-hydroperoxide, per-acid or ester of a per-acid; (b) an organic reducing agent; and (c) a boron compound such as boric oxide, a boric acid, e.g. orthoboric or metaboric acid, or a borate ester. The invention includes within its scope a process for the polymerisation of acrylonitrile, alone or in admixture with another vinyl monomer which comprises contacting acrylonitrile, and other vinyl monomer (if any), in solution with the new polymerisation initiator.

The hydroperoxides, hydroxy-hydroperoxides, per-acids and per-esters which may be used as the peroxy compound may be selected from amongst those mentioned in Houben-Weyl, Methoden der organischen Chemie, Makromolekulare Stofre 14/ 1, pp. 231 to 243. Examples of suitable compounds are t-butyl hydroperoxide, cyclohexyl hydroperoxide, cumyl hydroperoxide, pinane hydroperoxide; methyl ethyl ketone hydroperoxide, cyclohexanone hydroperoxide, methyl hydroxy-hydroperoxide, diethyl ketone hydroperoxide, and performic, peracetic and perbenzoic acids. These per-acids may be used preformed or may be prepared in situ from hydrogen peroxide and the corresponding acid. Suitable per-esters include methyl ethyl or t-butyl peracetate or t-butyl perbenzoate.

The organic reducing agent (b) may be any of those normally used in redox polymerisation systems. Suitable compounds are sugars such as glucose, benzoin, dihydroxyacetone, ascorbic acid, tartaric acid, lactic acid, citric acid, and stannous oxalate.

The boron compound may be boric oxide or a boric acid. The alkyl, cycloalkyl, alkylcycloalkyl, aryl, alkylaryl and aralkyl orthoborates and metaborates may also be used, especially methyl, ethyl, propyl, amyl, cyclohexyl, phenyl and benzyl orthoborates.

In the new initiators the peroxide is normally used in a proportion of 0.01 to 5% of the weight of the monomer, preferably 0.1 to 2%. The reducing agent is used in an amount substantially equimolecular to the peroxide, and the boron compound is used in an amount such that there is at least 0.01 mol, and preferably 0.1 to 1 mol, of boric acid or boric acid equivalent per peroxide group. A ratio greater than 1 only very slightly changes the degree of conversion of the monomer within a given time.

The organic solvents normally used as solvents for the polymerisation of acrylonitrile may be used as the polymerisation medium in the presence of the new initiators. Dimethylformamide, dimethylsulphoxide, ethylene glycol carbonate and propylene glycol carbonate may be more especially mentioned.

The polymerisation temperature may vary Within quite wide limits depending on the various components of the initiator system. It may for example be from 20 to C. Similarly the pressure may be at, below or above atmospheric pressure, though there is rarely any advantage in operating other than at atmospheric pressure. The atmosphere above the reaction medium should be inert, e.g. nitrogen.

The new initiators are not only suitable for the solution polymerisation of acrylonitrile, but also for its copolymeri sation with monomers having at least one polymerisable vinyl group CH =C Suitable such monomers include acrylic and methacrylic esters (e.g. methyl acrylate and methacrylate); acrylic and methacrylic amides; acrylic and methacrylic acids; unsaturated sulphonic acids (e.g. p-vinylbenzenesulphonic and p-vinyloxybenzenesulphonic acids); vinyl esters (e.g. vinyl acetate or benzoate); allyl esters (e.g. allyl acetate); and vinyl-aromatic compounds (e.g. styrene and p-methylstyrene). Normally the proportion of such copolymerisable monomer or monomers will not be more than 1 mol per mol of acrylom'trile.

The following examples illustrate the invention.

EXAMPLE 1 The apparatus used consists of a cylindrical 500 cm. glass reactor fitted with a stainless steel blade stirrer revolving at 220 r.p.m., a reflux condenser fitted at the top with a bubble-counter, a thermometer sleeve and a dropping funnel having a nitrogen inlet below the tap.

Before introducing the reagents the apparatus is purged by sweeping it with a stream of nitrogen for 30 minutes. 100 g. of acrylonitrile and g. of dimethylformamide are then introduced while the stream of nitrogen at the top of the condenser is maintained. The apparatus is then immersed in a tank containing water maintained at 60 C. by a thermostat. When the temperature of the contents of the reactor reaches 60 C., 0.86 g. of cyclohexyl hydroperoxide (i.e. 7.4 10- mol), 1.31 g. of ascorbic acid (7.4 10- mol) and 0.47 g. of orthoboric acid (7.4x 10- mol) dissolved in 5 g. of dimethylformamide are introduced with stirring. The mixture is allowed to react for 5 hours under these conditions, and a thick polymer solution is obtained. To determine the yield an aliquot portion representing /s of the reaction mixture is introduced into 300 cm. of distilled water with stirring. The polymer precipitates as fine particles which are filtered oif, Washed on the filter with 800 cm. of boiling distilled water, sucked dry, and dried in an oven at 60 C. under a pressure of 50 mm. Hg.

From this aliquot portion 14.8 g. of a polymer of specific viscosity 0.115 (measured at 25 C. on a solution in dimethylformanmide containing 2 g. of polymer per De me of litre) are obtained. cr inver- Working under the same conditions but at 50 C., the i gg AS rbic Cid B m acid 1x degree of conversion is 39% and the specific viscosity P60 8 Co a o 0.140. 1 g. (5.9 10 mol) 1.035 g. (5.0 10 0.305 g. (5.0 10 60 h b f? pti carried oglitfing either 5 1g. (5.9X10- ml). 1.03 1g. 5.0 s 0 t e on aci r s mo c f Cor 1c acld or M no polym 1 (5 9 10-s 1) Ni 0,3 5 0 erlsation o acry onitri e occurs. (5 9 10-3 1) Nil Ni] 0 EXAMPLE 2 EXAMPLE 5 A series of experiments is carried out as in Example 1 10 o but at 70 C. using, in solution in 5 g. of dimethylform- A Senes of expenfnents 1s earned Q at Q m h amide, the initiators given in the Table below, which also aPParatuS as Example W1th i ,lmtlators m solution in 5 g. of dimethylformamide being in each case gives the results obtained.

as given in the table below, which also glves the results obtained: Degree of convor- Degree of $1011, convert-Butylhydroperoxide Ascorbic acid Boric acid percent sion, per- Hydrogen peroxide Ascorbic acid Boric acid cent 1 g. (11.1X10- mol) 1.90 g. 11.1 10 0.7 g. (11.1X10-3 68 mol mol.) 0.4 g. (1i.7 10 moi)- 2.07 g. (11.70 10 8 0.73 g. (11.7 10 5s 1 g. (11.1 10 mol)..- Nil Nil a mol). mol. 1 g. (11.1 10 moi)-.. 1.96g Nil 4.5, 0.4 g. (11.7X10- m01) 2.07 g. (11.7 10 Nil. 3 1 g. (11.1)(10- mol).-. Nil 0.7g 4 mol).

0.4 g. (11.7)(10- moi)- gfs g 1. I EXAMPLE 3 04g 1 7X 0 mo) 1 1 A Series of experiments is carried out as in Example 1 ofg;1ot2hg $111331 a 120 volume aqueous solution, 1.e. containing 11.6 mols but at 70 C. The initiators, used in solution in 5 g. of 1L6 mols of H202 per htre dlmethylformamide are as given in the table below, which EXAMPLE 6 also gives the results obtained:

Polyacrylonitrile is obtained 1n a yield of 13% by Working as in Example 1 at a temperature of C. Degree and using an initiator consisting of hydrogen peroxide Oumene hydm gfi gg (0.4 g., 11.7 10 mol), glacial acetic acid (11.7)(10' peroxide Ascorbic acid Boric acid percent mol), ascorbic acid (2.07 g. ll.7 10 H101), and boric l1.7 10- mol). 0.7g. (5.6)(10- mo1)- 0.81g. (4.0x10 3 0.285 g. (4.6X10 3 acld (0 73 g 1 mol 3 incl). 35 In the absence of bone acid, or m the presence of the g N11 0 hydrogen peroxide/acetic acid couple only, no polymer 0.7g. (4.6Xl0- mo1) Nil- 14 forms. 0.7 g. 4.s 10- mol) Nil--- 0 EXAMPLE 7 Working as in Example 1, at the temperatures and X 5 4 with the initiators indicated in the table below, the results E MPLE 4 given in the same table are obtained, which show the A series of experiments is carried out at 50 C. in the effect of boric acid on systems consisting of ascorbic acid same apparatus as in Example 1, with the initiators in and various peroxides.

Degree 01' C011- Iemperversion, Peroxides ature, C. Ascorbic acid Boric acid percent. Mghy; ethyl ketone hydroperoxide* 50 1 g. (5.69X10-3 mol) 0.5 g. (8.05))(10- moi). 64

g. 5 Do 50 1 g. (569x10 mol) Nil 3 t-Butgl peracetate (1 g. 7.6)(10- 1.33 g. (7.6X10- mo1)- 0.47 g. (7.6X10- n10l)". 77

m0 Do 60 1.33 g. (7.6)(10- mol).-- Nil. 0 t-Butgl perbenzoate (1 g. 5.15 10 60 0.91 g. (5.15X10-3 mol) 0-32 g. (5.15 10- mol)..- 53

Do 60 0.91 g. (5.15X10 mol) Nil 0 *Used as a 50% solution in dimethyl phthalate. The hydroperoxide consists of a mixture of hydr0xy-2-hyd10peroxy-butane and of 2,2-bis(hydropei'oxy) butane in an undetermined EXAMPLE 8 A series of experiments is carried out as in Example 1 using dimethylsulphoxide (195 g.) in place of dimethylformamide with the initiators indicated in the following table, which also shows the results obtained.

Degree Temperof conature, version, Peroxides C. Ascorbic acid Boric acid percent Cyclohexyl hydroperoxide (0.86 g., 60 1.31 g. (7.4X10- mol) 0.47 g. (7.4.X10- mol) 7.4X10" mol) Do 60 1.31 g. (7.4X10" mol) Nil 0 ciing l hfsdroperoxide (0.7 g., 4.6x 0.81 g. (4.6)(10- mol).. 0.285 g. (4.6)(10' mol)--- o 70 0.81 g. (4.6Xl0- mol) Nil 0 t-ll3igyl hgdroperoxide (1 g., 11.1X 70 1.96 g. (11.1X10' mol).-- 0.7 g. (11.1)(10' mol) 74 mo Do 70 1.96 g. (11.1X10' 11101)... Nil 0 t-Butgl perbenzoate (1 g., 5.15X10' 60 0.91 g. (5.15X10- mol)-.. 0.32 g. 15x10" mol) 67 Do 60 0.91 g. (5.15X10' mol) Ni1-- 0 Pilrbar ie hgdroperoxide (1 g., 5.9x 50 1.036 g. (5.9X10 moi)-.. 0.365 g. (5.9)(10- mol)..-

- mo Do 50 1.036 g. (5.9)(10- moi)--- Nil. 0

EXAMPLE 9 A series of polymerisation experiments is carried out as in Example 1 with the initiators being as given in the table below, which also gives the results obtained.

I claim:

1. Process for the polymerization of a monomer system comprising acrylonitrile, alone or in admixture with another vinyl monomer in a proportion not exceeding 1 mol per mol of acrylonitrile, which comprises contacting Temper- Degree of ature, Ascorbic conversion,

Boron compound C. Solvent Peroxide acid, g. percent Methyl borate (0.53 g., 5.l5 10- mol) 60 Dimethy1sulphoxide t-Butyl perbenzoate 1 1 0. 91 82 Amyl borate (1.4 g., 5.15X 11101) 60 ...d0 d0. Z 0. 91 90 B 0 (2.57x10- mol) 60 Dimethy1formamide do. 2 0. 91 70 Methyl borate (0.8 g., 7.4)(10- mol) 50 .-..do yclohexyl hydroperoxide 4 1. 31 65 1 1 g., 5.15 1o mol. 2 5.15X10- mol.

3 0.86 g., 7.4Xl0" mol. 4 7.4X10- mo1.

EXAMPLE 10 Example 1 is repeated using, as initiators, butyl perbenzoate (1 g., 5.15 10 mol), benzoin (5.15Xl0 mol), and orthoboric acid (5.15x 10- mol). The degree of conversion obtained is 26%. With no benzoin, no polymerisation takes place.

EXAMPLE 11 The experiment of Example 1 is repeated with, as initiator, t-butyl perbenzoate (l g., 5.15 X10" mol), ascorbic acid (0.91 g., 5.l5 10- mol), and the various amounts of boric acid given in the following table so as to vary the molar ratio of boric acid/redox system. The results obtained are given in the table below.

A series of experiments is carried out as described in 50 Example 1, the monomers and therr amounts, the initiators and the temperature in each experiment being as given in the table below, which also indicates the results obtained:

the said monomer system at 20 to 100 C., in solution in dimethylformamide, dimethylsulphoxide, ethylene glycol carbonate, or propylene glycol carbonate with a polymerization initiator comprising (a) 0.01 to 5% by weight of the monomer or monomers of a peroxy compound selected from the group consisting of hydrogen peroxide, a hydroperoxide, a hydroxy-hydroperoxide and a per-acid and an ester thereof, (b) an organic reducing agent selected from the group consisting of glucose, benzoin, dihydroxyacetone, ascorbic acid, tartaric acid, lactic acid, citric acid and stannous oxalate in an amount substantially equimolecular to the peroxy compound, and (c) a boron compound selected from the group consisting of boric oxide, a boric acid, and a lower alkyl borate in a proportion of 0.01 to 1 mol per mol of peroxy group equivalent.

2. Process according to claim 1, in which the organic reducing agent is ascorbic acid.

3. Process according to claim 1, in which the organic reducing agent is benzoin.

4. Process according to claim 1 in which the peroxy compound is cyclohexyl hydroperoxide.

5. Process according to claim 1 in which the peroxy compound is t-butyl hydroperoxide.

6. Process according to claim 1 in which the peroxy compound is cumene hydroperoxide.

7. Process according to claim 1 in which the peroxy compound is pinane hydroperoxide.

8. Process according to claim 1 in which the peroxy compound is peracetic acid.

9. Process according to claim 1 in which the peroxy compound is methyl ethyl ketone hydroperoxide.

e p Degree of Ascorbic conversion, Monomers C. Solvent, g. Peroxldes acid, g. Boron derivative percent Acrylonltrile, 95 g.; methyl methacry- Dimethylform- Cumene hydro- 2 0.99 Methyl borate 3 77 late, 4 g.; potassium p-vinyloxybenamide, 200 peroxide. zene sulphonate, 1 g.

D0 6O Dimethylsult-Butyl perbenzoate 6 0.91 Boric acid 6 93 phoxide, 200. Acrylonitrile g.; vinylidene chloride, 50 Dimethylform- Methyl ethyl ketone B 1 Methyl borate 9 62 20 g. amide, 200. hydroperoxide, l g.

200 .dO 5 1 0 Methyl ethyl ketone i 1 Methyl borate, 0.84 g..-- 63 Acrylonitrile, 80 g.; vinyl acetate, 20 g-. 50 do hydroperoxlde, 1 g.

do 5 1 Nil 15 Methyl ethyl ketone B 1 Methyl borate, 0.84 g 62 Acrylonitrile, 80 g.; styrene, 20 g 50 .....d0 hydroperoxrde, 1 g.

.do 1 Nil 31 Methyl ethyl ketone 1 Methyl borate, 0.84 g 44 Acrylonitrile, 50 g.; styrene, 50 g 50 do hydroperoxlde, 1 g.

. o 1 Nil 22 1 0.86 g., 5.65X10- mol. B 0.32 g., 5.15X10- mol. 2 5.65X10- mol. 7 As a 50% solution in dimethyl phthalate. 3 0.8 g., 7.7X10' mol 8 5.69X10" mol. 4 1 g., 5.15X10- mol 9 0.84 g., 8.1Xl0- mol. 5 5.15X10- mol.

10. Process according to claim 1 in which the peroxy 3,222,429 12/ 1965 Boyd et a1. compound is t-butyl peracetate. 3,251,810 5/1966 Buning.

11. Process according to claim 1 in which the peroxy 3,275,611 9/1966 Mottus et a1. compound is- S-butyl perbenzoate.

12. Process according to claim 1 in which the peroxy 5 OTHER REFERENCES compound is hydrogen peroxide.

References Cited UNITED STATES PATENTS 3,025,284 3/1962 George etal. 3,060,157 10/1962 Goodman et a1. 252426; 260--29.1,30.8, 32.6, 47, 79.3, 88.7

HARRY WONG, JR., Primary Examiner Okuda et al., Chem. Abs., 54 (1964), p. 7235i. 

